Double exhaust gas blast circuit breaker



Oct. 7,1969

P. BARKAN 3,471,667

DOUBLE EXHAUST GAS BLAST CIRCUIT BREAKER n Filed July 21, 1967 2Sheeis-Sheet l PH/L/P BAR/(AN,

BY A/am um ATTORNEY United States Patent O 3,471,667 DOUBLE EXHAUST GASBLAST CIRCUIT BREAKER Philip Barkan, Media, Pa., assignor to GeneralElectric Company, a corporation of New York Filed July 21, 1967, Ser.No. 655,146 Int. Cl. H01h 33/82, 9/44, 33/18 U.S. Cl. 200--148 6 ClaimsABSTRACT OF THE DISCLOSURE Background of the invention This inventionrelates to a gas blast circuit breaker and, more particularly, to meansfor improving the interrupting ability of such a circuit breaker.

The usual gas blast circuit breaker comprises means for establishing anelectric arc across the gap between two electrodes and means fordirecting a high velocity blast of gas into the arcing region. Thepurpose of this blast is to cool the arc and to scavenge the arcingregion of arcing products so as to increase the rate at which dielectricstrength is built up across the gap when the current zero point isreached. By increasing the rate of dielectric recovery, it is possibleto improve the ability of the gap to withstand the usual recoveryvoltage transient that builds up as soon as current zero is reached,thus improving the interrupting ability of the circuit breaker.

A common type of gas blast circuit breaker is the axial blast type. Insuch a breaker, the blast of gas ilows axially of the arc, first passingthe one electrode Which is normally referred to as the upstreamelectrode and then passing the other electrode, which is referred to asthe downstream electrode. It has been found that the interruptingcapacity of the axial blast type circuit breaker can be increased byproviding an auxiliary blast passage in the upstream electrode and bydirecting an auxiliary blast from the arcing region through theauxiliary blast passage during interruption. But it has been found alsothat the ability of such a circuit breaker to interrupt capacitivecurrents which typically are only several hundred amperes or less, isimpaired by such an auxiliary blast.

Summary Accordingly, an object of my invention is to provide simple,reliable, high-speed control means which can produce an auxiliary gasblast from the arcing region through the upstream electrode for highcurrent interruptions and yet does not detract from the ability of thebreaker to interrupt capacitive currents.

Another object is to provide control means of this type which can openan auxiliary blast Valve before the main blast valve opens and beforethe contacts part during a circuit interrupting operation.

Another object is to provide control means of this gen- 3,471,667Patented Oct. 7, 1969 eral type which effects closing of the auxiliaryblast valve immediately after a circuit-interrupting operation, therebypreventing waste of pressurized gas.

In carrying out my invention in one form, I provide a pair of contactsthrough which current passes when the circuit breaker is closed, thecontacts being separable to initiate an arc therebetween. Adjacent thecontacts is a pair of spaced electrodes onto which the arc istransferred. Means is provided for causing a main blast of gas to passaxially of the arc during both high and low current interruptions. Anauxiliary blast passage extends through the electrode located upstreamfrom the arc lwith reference to said main blast. A normally-closedauxiliary -blast valve is provided for controlling ilow through saidauxiliary blast passage and is openable to produce an auxiliary blastfrom said arcing region through said auxiliary blast passage. Theauxiliary blast valve is controlled by electroresponsive meansresponsive to overcurrents through said contacts even before said arc isinitiated for opening said auxiliary blast valve during high currentinterruptions. Means is provided for maintaining said auxiliary blastvalve closed during low current interruptions.

Brief description of drawings For a better understanding of theinvention, reference may be had to the following description taken inconjunction with the accompanying drawings, wherein:

FIG. l is a sectional view through a circuit breaker embodying one formof my invention.

FIG. 2 is a sectional view of a portion of FIG. l.

FIG. 3 is a sectional view along'the line 3-3 0f FIG. 2.

Detailed description of preferred embodiment Referring now to FIG. l,the circuit interrupter shown therein is of the sustained-pressure,gas-blast type described and claimed in U.S. Patent 2,783,338, Beatty,assigned to the assignee of the present invention. Only those parts ofthe interrupter that are considered necessary to provide anunderstanding of the present invention have been shown in FIG. 1. Inthis respect, only the right hand portion of the interrupter has beenshown in section inasmuch as the interrupter is generally symmetricalwith respect to a Vertical plane and the left hand portion issubstantially identical to the right hand portion. As described indetail in the above-mentioned Beatty patent, the interrupter comprises acasing 12 which is normally iilled with pressurized gas to define aninterrupting chamber 11. Located within the interrupting chamber 11 area pair of relatively movable contacts 14 and 16 which can be separatedto draw an arc within the pressurized gas within the chamber 11. Thecontact 14 is relatively stationary, whereas the other contact 16 ismounted for pivotal motion about a xed, current-carrying pivot 18.Stationary contact 14 is mounted on the inner end of a high voltageterminal bushing 7 comprising two porcelain shells 8 and 8a and aconductive stud 9 extending therethrough. When movable contact 16 isdriven clockwise about pivot 18 from its solid-line closed position ofFIG. l, an arc is established in the region where the contacts part. Themovable contact 16 is shown by dotted lines in FIG. l in apartially-open position through which it passes during acircuit-interrupting operation after having established an arc.

Movable contact 16 is supported by means of its current-carrying pivot18 on a conductive bracket 19 that is preferably formed integral with astationary cylinder 32. Cylinder 32 at its lower end is suitablysupported from a generally cylindrical casting 33. Casting 33 at itslower end is suitably secured to a flange 35 rigidly carried by thestationary metallic casting 12.

For producing a gas blast to aid in extinguishing the arc, cylindricalcasting 33 contains a normally-closed exhaust passage 36 leading fromthe interrupting chamber 11 to the surrounding atmosphere. Casting 33 atits upper end is provided with a tubular nozzle member 38 having anorifice portion 39 at its outer end defining an inlet 37 to the exhaustpassage 36. This inlet 37 is referred to hereinafter as the orificeopening. The flow of arc-extinguishing gas through tubular nozzle 38 andexhaust passage 36 is controlled by means of a cylindricallyshapedreciprocable blast valve member 40 located at the outer, or lower, endof exhaust passage 36. This blast valve member 40 normally occupies asolid-line, closed position wherein a portion 42 at its lower endsealingly abuts against a stationary valve seat 34 carried by exhaustcasting 33.

During a circuit interrupting operation, movable blast valve member 40is driven upwardly from its solid-line, closed position of =FIG. lthrough a partially open intermediate position shown in dotted lines inFIG. l. Opening of valve member 40 allows pressurized gas in the chamber11 to ow at high speed through orifice opening 37 and nozzle 38 and outexhaust passageway 36 past valve member 40 to atmosphere, as indicatedby the dotted line arrows B of FIG. 1. The manner in which the gas blastacts to extinguish the arc will soon be described in greater detail.

At its upper end, the cylindrical blast valve member 40 surrounds aprojecting cylindrical support 41 upon which the valve member 40 issmoothly slidable. The support 41 is fixed to the casting 33 by suitablemeans (not shown). A suitable compression spring (not shown) positionedbetween the movable valve member 40- and the lower end of support 41tends to hold the valve member 40 in its closed position against thevalve seat 34.

To protect support 41 and the upper end of valve mernber 40 from theharmful effects of arcing, a protective metallic tube 43 is positionedabout these parts and is suitably secured to support 41. Secured to theouter surface of this tube is a downstream probe or electrode 45,preferably of a refractory metal, which projects radially from tube 43and transversely into the path of the gas blast flowing throughpassageway 36. As will soon appear more clearly, the downstream terminalof the arc is transferred to this electrode 45 during an interruptingoperation and, after such transfer, occupies an instantaneous positiongenerally corresponding to that shown at 46. The downstream electrode ispreferably constructed as shown and claimed in Patent No. 2,897,324,Schneider, assigned to the assignee of the present invention, so that ithas a nonstreamlined upstream surface 48 that coacts `with the gas blastto form a stagnation region upstream from the surface 48. The terminalof an arc such as 46 reaching the electrode 45 is captured within thestagnation region and thus prevented from being driven furtherdownstream by the gas blast.

For controlling the operation of movable blast valve 40 and movablecontact 16, a combined operating mechanism 50 is provided. Thismechanism 50 is preferably constructed in the manner disclosed andclaimed in the aforementioned Beatty Patent 2,783,338, and its detailsform no part of the present invention. Generally speaking, thismechanism 50 comprises a blast valve-controlling piston 51 and acontact-controlling piston 52 mounted within the cylinder 32. Blastvalve-controlling piston 51 is coupled to movable blast valve member 40through a piston rod 54 suitably clamped to valve member 40. Thecontact-controlling piston 52, on the other hand, is connected to themovable contact 16 through a piston rod 58 and a cross head 59 securedto the piston rod. A link 60 pivotally poined to the cross head 59 at 61and to the movable contact 16 at 62 interconnects cross head 59 andmovable contact 16. When blast valve-controlling piston 51 is drivenupwardly, it acts to open blast valve member 40, and, simultaneously, todrive contact-controlling piston 52 upwardly to produce opening movementof the movable contact member 16.

Opening movement of contact member 16 first establishes an arc betweenthe ends of the contacts 14 and 16. Shortly thereafter, however, theblast of gas which has been flowing through the orifice opening 37, asindicated by the dotted-line arrows B, forces the upstream terminal ofthe arc on to an upstream arcing electrode 70, which is electricallyconnected to the stationary contact 14. As opening motion of movablecontact 16 continues, the gas blast forces the downstream terminal ofthe arc to transfer from the movable contact 16 to orifice structure 39,which is electrically connected to the movable contact 16. The gas blastthen impels the downstream terminal of the arc through the orificeopening 37 and nozzle 38 on to the upper end of the protective metallictube 43. From there, the gas blast drives the downstream arc terminaldownwardly and into the previously-described stagnation region adjacentthe upstream surface y48 of the electrode 45. The arc then occupies theposition generally shown at 46. When the arc is in this position, thearc column extends through the orifice opening 37 and is subjected tothe cooling and deionizing effect of the axial blast.

After completion of the interrupting operation, the blast valve 40 isreturned to its closed position of FIG. l by the operating mechanism 50while the contacts 14, 16 remain open.

It has been found that the circuit-interrupting capacity of the circuitbreaker of FIG. l can be increased by directing an auxiliary blast fromthe arcing region through the upstream electrode during thecircuit-interrupting operation. For accommodating this auxiliary blast,I provide an auxiliary blast passage 9S, 96 leading through the upstreamelectrode 70 and the hollow stud 9 to atmosphere. The portion of thisauxiliary blast passage that extends through electrode 70 is designated95 and the portion extending through 4stud 9 is designated 96.

The auxiliary blast passage is normally closed by means of anormally-closed auxiliary blast valve comprising a movable valve member92 cooperating with a valve seat 93 in a partition 94. But under highcurrent conditions, as will soon be described, the movable Iauxiliaryblast valve member 92 is moved to the left to open the auxiliary blastvalve 90. This permits high pressure air to flow through the auxiliaryblast passage 95, 96 to atmosphere via the then-open auxiliary blastvalve 90. The path of the auxiliary blast is indicated by the arrows 97in FIG. 1.

The auxiliary blast passage is dimensioned so that a much smaller flowpasses therethrough than through the main blast passage 36 (assumingthat both blast valves are open). The entrance to the auxiliary blastpassage 95, 96 is through a restricted orifice 98 in the upstreamelectrode 70 which is designed to produce sonic velocity in this region.The orifice 98 is the principal and controlling restriction in theauxiliary blast passage when the auxiliary blast valve is open.

For operating the movable valve member 92 of the auxiliary blast valve,I provide (as shown in FIG. 2) a piston 99 connected to the movablevalve member and slidably mounted in a cylinder 100. A spring 101 actingupon piston 99 urges the valve member 92 toward open position, butpiston 99 is normally held in the valveclosed position shown bypressurized air acting on its upper surface. This pressurized air isderived from the interior of tank 12 through a control conduit 102, 103.

For controlling the flow of pressurized air through conduit 102, 103, Iprovide a pilot valve schematically shown at 104. When the movable valveelement 105 of pilot valve 104 is in its illustrated position, freecommunication is afforded between the pressurized tank 12 and cylinderspace 107 above piston 99. But when the movable valve member 105 isrotated counterclockwise by 90 degrees, cylinder space 107 is isolatedfrom the pressurized tank and is instead connected to atmosphere throughconduit 110. This dumps the pressurized air above piston 99 and permitsspring 101 to drive piston 99 and valve member 92 upwardly, therebyopening the auxiliary blast valve 90.l

To close the auxiliary blast valve 90, the pilot 'valve member 105 isrotated in an opposite direction, returning it to its position of FIG.2. This reestablishes high pressure above piston 99, forcing it downwardand carrying valve member 92 into its closed position of FIG. 1. The-space beneath piston A99 is vented to atmosphere through passage 111,and therefore piston 99 can freely return to its closed position whenhigh pressure air is supplied to cylinder space 107.

For controlling the movable pilot valve member 105, I provideelectroresponsive operating means 115 which is responsive to themagnitude of the current through conductive stud 9. This operating meanscomprises a magnetizable core 116 xedly mounted around the stud 9.Referring to FIG. 3, core 116 has a gap 117 therein and an armature 118is located near the gap. When the current through stud 9 exceeds apredetermined value, the flux density in the gap 117 becomes high enoughto pull the armature 11'8 downwardly into the gap, thereby operating alinkage 120 that actuates pilot valve 104.

Referring to FIG. 2, linkage 120 comprises a bell crank 122 mounted on astationary pivot 124 and having one arm pivotally connected to armature118 and its other arm connected to movable pilot valve element 105. Theconnection to movable pilot valve element 105 is through an operatingrod 125 that is pivotally connected at its opposite end to the movablepilot valve element 105 and the bell crank 122, respectively. A resetspring 127 normally holds the parts in the position of FIG. 2.

When the current through stud 9 exceeds a predetermined value, e.g.,twice the continuous current rating of the circuit breaker, a suicientdownward magnetic force is developed on armature 118 to move itdownwardly against the bias of yspring 127. This pivots bell crank 122counterclockwise, driving operating rod 125 to the left and rotatingpilot valve member 105 counterclockwise into its venting position. Thespring 101 responds by driving piston 99 and blast valve member 92upwardly into open position, thereby opening the auxiliary blast valve90 and producing the auxiliary blast through the upstream electrode.

Although the above-described auxiliary blast substantially improves thedielectric recovery rate for high currents, such as fault currents, ithas been found through extensive study and tests that it detracts fromthe ability of the circuit breaker to switch capacitive currents, whichtypically are only several hundred amperes or less. As explained in U.S.Patent 2,391,672, Boehne et al., assigned to the assignee of the presentinvention, interruption of such a current at current zero is followed bya relatively slow voltage buildup to: a value approaching twice normalcrest voltage. lFor some reason, not fully understood, the auxiliaryblast appears to detract from the circuit breakers ability to withstandthis voltage, even though it substantially increases its 'ability tohandle the much steeper voltage rises following current zero during theinterruption of an inductive circuit of high currents. To improve theability of the circuit breaker to handle capacitive currents, I controlthe auxiliary blast valve in such a manner that it opens only inresponse to relatively high currents, remaining closed for low currents,as described hereinabove. In a typical circuit breaker, I open theauxiliary blast valve only when the current exceeds about 5,000 amperes.Capacitive currents are typically only as high as several hundredamperes. So it will be evident that no auxiliary blast is establishedduring capacitive switching operations. The operating current level forthe auxiliary blast valve 90 is established well above the continuouscurrent rating of the circuit breaker so that the highest normalcurrents will not cause the auxiliary bla-st valve to open.

It is important that the Iauxiliary blast valve be opened rapidly duringa high current interruption so that the auxiliary blast is available toaid in the arc-extinguishing process at the earliest possible moment.For a number of different reasons, my lauxiliary blast valve is capableof opening within an extremely short time from the instant at which highcurrent is initiated. One reason is that its moving parts are of alight-weight, low-mass construction, which construction is madepossible, in part, because these components are not required to carryany of the current through the interrupter. This lightweightconstruction permits high speed motion. Another reason why my auxiliaryvalve can open quickly is that the valve-operating mechanism can respondto .the current owing at all times through the interrupter. It is notnecessary to draw an arc or to transfer the arc to some part of theinterrupter before the valve-operating mechanism 115 can respond. It canrespond immediately whether an arc is present or not since it respondsto the current through stud 9, which represents the total currentthrough the interrupter. Nor is the valveoperating means dependent upona drop in tank pressure as a condition precedent to operation. Even ifthe main blast valve 40 is still closed and the pressure in tank 12 isat its normal high level, when the pilot valve 104 is operated, thespring 101 will produce opening of the auxiliary blast valve.

Nor does operation of the lauxiliary blast valve depend upon somedelicate balance between tank pressure and magnetic force, which couldbe detrimentally affected by a variation in tank pressure. IIn theillustrated arrangement, the operation of the pilot valve depends almostentirely on current level, and the operation of the auxiliary blastvalve follows immediately thereafter with little dependence on normaltank pressure variations. Reclosing the auxiliary blast valve islikewise a positive operation which does not depend upon a delicatebalance of tank pressure and magnetic force. As soon as the pilot valve104 is returned to its position of FIG. 2 in response to a drop incurrent, a high positive force is available to reclose the auxiliaryblast valve. The linkage and reset spring 127 are so adjusted thatreclosing of the auxiliary blast valve occurs at substantially the samecurrent level at which the valve opened.

Another advantage of my auxiliary blast valve control is that it is aself-contained unit which requires no coupling to the main movable partsof the circuit breaker or to their controls. This not only contributesto simplicity but also eliminates electrical insulation problems whichcould arise from the presence of an additional insulating part (i.e.,the coupling) subject to high voltage stress.

Sometimes it may be desired that the disclosed circuit breaker switchremain closed under fault current conditions while another circuitbreaker, e.g., one further down the line, opens to clear the fault. Itis recognized that passage of fault current through the illustratedcircuit breaker will cause the auxiliary blast valve 90' to open eventhough the circuit breaker itself does not open. But this is not asignificant disadvantage. The -small amount of air con-sumed by openingof the small auxiliary blast valve is negligible since this openingcontinues for only a very `short time inasmuch as the auxiliary blastvalve closes as soon as the fault is removed by the other breaker.

While I have shown and described a particular embodiment of myinvention, it will be obvious to those skilled in the art that variouschanges and modifications may be made without departing from myinvention in its broader aspects; and I, therefore, intend in theappended claims to cover all such changes and modifications as fallwithin the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An electric circuit breaker of the gas blast type comprising:

(a) a pair of contacts through which current passes when said circuitbreaker is closed, said contacts being separable to initiate an arctherebetween,

(b) a pair of spaced-apart electrodes onto which the respectiveterminals of said arc are transferred during an interrupting operation,

(c) an oriiice having an opening through which said arc is adapted toextend when present between said electrodes,

(d) means for causing a main blast of gas to pass through said orificeopening axially of said arc about the arc periphery during both high andlow current interruptions,

(e) an auxiliary blast passage extending through the electrode locatedupstream from said orice with reference to said main blast,

(f) a normally-closed auxiliary blast valve for controlling iiow throughsaid auxiliary blast passage and openable to produce an auxiliary blastfrom the region of said arc through said auxiliary blast passage,

(g) means responsive to current through said contacts above apredetermined value even before said arc is initiated for opening saidnormally-closed auxiliary blast valve during high current interruptionsto produce an auxiliary blast through said auxiliary blast passageduring high current interruptions,

(h) and means for maintaining said auxiliary blast valve closed duringlow current interruptions.

2. The circuit breaker of claim 1 in which a conductive part is providedthrough which passes substantially all current iiowing through saidcircuit breaker via either said contacts or said electrodes, saidcurrent-responsive means being controlled by the current passing throughsaid conductive part.

3. An electric circuit breaker of the gas blast type comprising:

(a) a pair of contacts through which current passes when said circuitbreaker is closed, said contacts being separable to initiate an arctherebetween,

(b) a pair of spaced-apart electrodes onto which the respectiveterminals of said arc are transferred during an interrupting operation,

(c) an orice having an opening through which said arc is adapted toextend when present between said electrodes,

(d) means for causing a main blast of gas to pass through said oriceopening axially of said arc about the arc periphery during both high andlow current interruptions,

(e) an auxiliary blast passage extending through the electrode locatedupstream from said orifice with reference to said main blast,

(f) a normally-closed auxiliary blast valve for controlling flow throughsaid auxiliary blast passage and openable to produce an auxiliary blastfrom the region of said arc through said auxiliary blast passage,

(g) an electroconductive part through which passes substantially allcurrent passing through said circuit breaker via either said contacts orsaid electrodes,

(h) a core mounted in close proximity to said electroconductive part andforming a magnetic circuit for iiux developed by current passing throughsaid electroconductive part,

(i) means for opening said normally-closed auxiliary blast valve whenthe ux in said magnetic circuit reaches a predetermined densityindicative of current through said conductive part reaching apredetermined value,

(j) and means for maintaining said auxiliary blast valve closed duringlow current interruptions.

4. The circuit breaker of claim 3 in which the means for opening saidnormally-closed auxiliary blast valve comprises a pilot valve operableto eilect opening of said auxiliary blast valve and means for operatingsaid pilot valve when the flux in said magnetic circuit reaches saidpredetermined density.

5. The circuit breaker of claim 3 in which:

(a) said core is mounted about said electroconductive p-art and anarmature is mounted nearby for movement in response to the flux reachinga predetermined density, and p (b) the means of limitation (i) comprisesa linkage responsive to the motion of said armature.

6. The circuit breaker of claim 3- in which:

(a) said core is mounted about said electroconductive part and anarmature is mounted nearby for movement in response to the flux reachinga predetermined density, and

(b) the means of limitation (i) comprises a pilot valve connected tosaid armature and operable by motion of said armature for effectingopening of said auxiliary blast valve.

References Cited UNITED STATES PATENTS 2,459,600 1/1949 Strom. 3,206,5829/1965 Jussila 200-148 3,214,551 10/1965 Taylor 20D-148 3,257,533 6/1966Leeds. 3,270,173 8/1966 Barkan. 3,278,711 ll/1966 Thuries et al.3,291,946 12/1966 Schubert 200-148 3,345,486 10/1967 Colclaser et al.3,418,440 12/1968 Beatty et al. 20G-147 ROBERT S. MACON, PrimaryExaminer U.S. Cl. X.R.

